Nutritional News: What 20 Studies Say About Eating a Handful of Nuts a Day

October 11, 2026

Independent research, explained simply. This article describes a published study. It is not a claim about any Sun & Seed product.

The paper

Aune D, Keum N, Giovannucci E, Fadnes LT, Boffetta P, Greenwood DC, Tonstad S, Vatten LJ, Riboli E, Norat T. Nut consumption and risk of cardiovascular disease, total cancer, all-cause and cause-specific mortality: a systematic review and dose-response meta-analysis of prospective studies. BMC Medicine, 2016;14:207. Read it free: doi.org/10.1186/s12916-016-0730-3.

The question

Do people who regularly eat nuts go on to have fewer heart problems, or live longer, than people who eat few or none? Many single studies had asked this, with answers that varied in size and certainty. An international team of researchers set out to pool them and see what the combined evidence says. We have covered only the heart and all-cause findings here; the paper reports other outcomes too, and you are welcome to read it in full.

How the study was done

This is a systematic review and meta-analysis, which means the researchers searched for every suitable earlier study using set rules and then combined their numbers into one overall estimate. Here the studies were all prospective cohorts: groups of people who reported their usual diet and were then followed over time to see who developed disease or died. Twenty studies (29 publications) were included, with up to 819,448 participants. Nine of the studies were from the US, six from Europe, four from Asia and one from Australia.

The key trick is a dose-response analysis. Rather than just comparing the highest and lowest eaters, the team worked out the change in risk for each extra 28g a day, which is one ounce, or a small handful.

What they found

Relative risk (RR) compares two groups. An RR of 0.71 means a 29% lower risk. A 95% confidence interval (CI) is the range in which the true value probably sits. If it includes 1, the result could be no effect at all. I² shows how much the studies disagreed with each other.

Coronary heart disease: RR 0.71 (95% CI 0.63 to 0.80), 11 studies, I² 47%. This analysis covered 12,331 cases of coronary heart disease.
Cardiovascular disease overall: RR 0.79 (95% CI 0.70 to 0.88), 12 studies, I² 60%.
Stroke: RR 0.93 (95% CI 0.83 to 1.05), 11 studies. The interval crosses 1, so a real effect could not be confirmed.
Death from any cause: RR 0.78 (95% CI 0.72 to 0.84), 15 studies, I² 66%, with 85,870 deaths in the analysis.

The curves were not straight lines. For coronary heart disease and all-cause death, most of the gain appeared at lower intakes, with little extra benefit above roughly 15 to 20g a day. More nuts did not keep lowering risk in step.

The authors also compared types. In the highest-versus-lowest comparison, all-cause mortality was lower for tree nuts (RR 0.80, 95% CI 0.74 to 0.86), peanuts (0.85, 0.81 to 0.89) and peanut butter (0.89, 0.80 to 0.99). The abstract describes the results as similar for tree nuts and peanuts.

The limits

Observational, not experimental. Nobody was assigned to eat nuts. The authors note that people who eat more nuts tend to smoke less, be leaner, be more active and eat more fruit and vegetables. Many studies adjusted for these factors and the links remained, but leftover confounding cannot be ruled out. The paper's own wording is careful: the estimated benefit applies "if the associations are causal".
The studies disagreed. Heterogeneity was high for cardiovascular disease (60%) and all-cause mortality (66%). The authors point to differences in age groups, location, how diet was assessed and what was adjusted for.
Food questionnaires are imperfect, and none of the included studies corrected for measurement error.
Possible publication bias. For all-cause mortality a statistical test suggested it (Egger P = 0.02), but the signal disappeared (P = 0.25) when five studies with fewer than 500 deaths were removed. The authors judged it unlikely to change the overall findings substantially.
Who was studied. Mostly adults in the US and Europe, with fewer from Asia and Australia.

What it does not show

It does not show that nuts cause better health, or that adding nuts to any one person's diet will change their risk. It does not tell us the best nut, because the paper found broadly similar results across tree nuts and peanuts. It says nothing about nut butters made from particular nuts, beyond the peanut butter figure above, and nothing about nuts eaten with added salt, sugar or coatings. Nor does it say how much is too much.

In our kitchen

For us, the practical reading is modest. In large groups of people followed over time, a small daily handful of nuts went along with better long-term outcomes, with the biggest step coming at fairly small amounts. In the kitchen that might be walnuts on porridge or almonds in a snack tin. The review looked at nuts as a food, not at any Sun & Seed product, so we make no claim for ours. If you have a nut allergy, this research is not for you.